Filament fault detector



June 8, 1965 v. E. GONSALVES ETAL 3,187,563

FILAMENT FAULT DETECTOR Filed March 13, 1961 INVENTORS VICTOR EMANUELGONSALVES GARRIT JOHANNES HILFERINK BY A ORBl;

United States Patent 24 6 9 Claims. (Cl. 73-160) This invention relatesto the preparation of packages of yarn comprising continuous filamentshaving a basis of a synthetic material. This invention further relatesto a method of and apparatus for signalling and registering the presenceof slubs on a running yarn or sheet of yarns.

In the textile industry, thebulk of the so-called semi or fullysynthetic continuous yarns produced are supplied to converters in theform of packages for processing into warp beams on Warping machines foruse in the weaving and knitting of fabric webs, and also for processingon other yarn holders such as pirns, bobbins, etc. In order to ascertainthe final quality of the fabric woven or knitted from said yarns, it isof great importance to know to what degree the yarn as delivered on thepackages is slubby.

In synthetic continuous filament yarn slubs are produced in the yarnmainly by the breakage of filaments. Where the broken ends project fromthe yarn slubs will normally form. The number of slubs. present in acertain length of yarn is in the main a measure of the processibility ofthe yarn. I

It is well known to employ certain scanning devices to obtain anestimate of the number of slubs in a sheet of yarns being wound onto awarp beam during a warping Operation. In this way the quality of theyarn can be evaluated without this making it possible, however, toimprove the qualtity of the final fabric. An investigation of theproblem has shown that the majority of slubs estab lished in a woven orknited fabric are present in a small proportion of the total number ofyarn threads of which said product is composed. The result of saidinvestigation has led to the fresh insight on which the presentinvention is based.

An object of the present invention is to provide a system forindicating, signaling and/ or registering the existence of slubs presenton a running length of yarn or sheet of yarns.

Another object of this invention is to provide an apparatus fordetecting broken filaments or slubs projecting from running yarn orsheet of yarns without engagement therewith.

Still another object of this invention is to provide a system fordetecting broken filaments on traveling yarn which does not requirefrictional engagement between the yarn and detecting means.

Other objects will appear from the following detailed description.

The present invention makes it possible to realize considerableimprovements in the qualtity of woven or knitted fabrics in asurprisingly simple manner.

In accordance with this invention each yarn package is provided with anindication of the number of slubs incorporated in the package duringwinding. Accordingly, the yarn packages to be placed on the creel of awarping or knitting machine can easily be classified according to thenumber of slubs. Consequently, the amount of first quality productfinally obtained increases with startingly rapid progress. Moreover, ithas been found possible to trace yarn packages containing many slubs totheir source. As a result, an improvement has been obtained inestablishing faulty machine operation responsible for the occurrence ofsaid slubs.

To enable the manufacture of yarn packages of the "ice above-describedtype to be carried out, there has been devised a method for signallingand/ or registering the existence of 'slu'bs on a running yarn or sheetof yarn, which is guided over two thread guides with the aid of atransport device. In a known method of signalling the existence of slubson a running sheet of yarn, a sheet of yarns is disposed in the shadowof a narrow obstruction intercepting a beam of light which is arrangedat right angles with and in the plane of said sheet of yarn. On the sideof the sheet of yarn away from the source of light there is a photocell.When a slub passes the light source, it will project beyond the path ofthe shadow and excite a signal in the photo-cell, which signal isthereupon amplified and registered.

This method is objectionable in that it becomes extremely costly whenapplied to a single running thread. Moreover, the apparatus required forthis purpose comprises equipment, such as the photo-cell and the lightsource, which is very fragile as well as liable to become obsolete,besides increasing the operating costs. Another objection is the largespace required to accommodate such apparatus.

The aforementioned drawbacks are not found in carrying out the methodaccording to the invention, wherein the yarn or the sheet of yarn ispassed over a short distance along one or more scanning membersconsisting of material of electrical conductivity, said devices beingpositioned between the thread guides and adapted to pass on an electricsignal transmitted thereto or induced therein to a device for theelectronic amplification and the signalling and/ or registration of theexistence of this signal.

Although this method is applicable to a sheet of yarn, it has been foundto be particularly advantageous when applied to a single running threadof yarn.

' In the interest of clarity, it is pointed out that a running yarn of asynthetic material is brought to a certain contact potential. Since thematerial of the yarn possesses practically all the properties necessaryfor properly insulating electric charges, the yarn retains theelectrostatic charge with which it has been furnished. Thischaracteristic holds for a slub on the yarn so that slub too is chargedin brushing the thread guides and retains the charge for a substantiallylong time.

In accordance with this invention a passing slub, i.e. a slub on arunning yarn, is detected by means of the electrostatic charge presenton the said slub. To this end scanning members of a scanning device areplaced so close to the running yarn that a projecting slub passes veryclosely along one or more of said members, or even brushes them. As aresult, the scanning device is furnished with a charge of the same signas the charge of the slub, thus creating a voltage impulse of the samesign each time the slub passes the scanning device. The voltage impulse,after it has been appropriately amplified, is fed to a signalling and/or registering means. The apparatus for signalling and/ or registeringthe existence of slubs on a running textile material comprises means formoving the textile material, two thread guides for guiding the textilematerial along a fixed path, and one or more scanning members of amaterial of electrical conductivity in one plane between the guides andat a short distance from the path of the running textile material. Thescanning members may be connected individually or in a group or groupsto one or more electronic amplifiers, the outputs of which are connectedto one or more signalling and/ or registering instruments.

The nature of the signalling and/ or registering instruments may varygreatly. The signalling instrument may be, for instance, a bell, asiren, or a lamp, which is energized when a passing slub has induced anelectric signal into one or more of the scanning members. The saidinstruments may also be connected to a stop motion, which discontinuesthe movement of the textile material. a

While the apparatus may be employed for detecting the passing of slubspresent in a sheet of yarn, as in the form of a warp, thebest resultswill be obtained where the apparatus according to the invention is usedfor counting the slubs on a single running thread of yarn, and will beso described. By counting may also be understood here the signallingand/or registering of the passing of slubs, if any, per unit of time orlength of the textile material.

The probability of a slub transmitting a signal is greatest where,according to the invention, the scanning'device or devices are arrangedsymmetrical in relation to the axis of the path of the yarn. If a singlescanning device is employed, it should preferably be circular.

Practice has shown, however, that there are various factors which mayinfluence the signalling operation unfavorably or even prevent thepassing of a slub from being signalled at all. Thus, it has been foundthat the electrostatic charge is very unequally distributed over thepassing yarn. The nature of said unequal charge distribution is twofold.In the first place the total charge displaces very irregularly along theyarn, as a result of which a very irregularly shaped signal issimultaneously induced into all the scanning members provided. It hasnot been found possible to separate this signal from that received froma passing slub by means of frequency sitters.

The electrostatic charge may also be distributed unequally over anycross-section of the thread of yarn. This results in an irregulararrangement in relation to the yarn path of the equipotential surfaceseffected by the electrostatic charge. If this irregular arrangement ofsaid equipotential surfaces varies very rapidly'and irregularly alongthe yarn axis, which will always happen, then the yarn itself willexcite varying induction voltages in the scanning members.

Surprisingly, it has been found possible to avoid the above drawbacksif, according to the invention, an even number of scanning members,located at an equal distance from the axis of the yarn path, is dividedinto two equally large interconnected groups which are each connected toan amplifier whose outputs are so connected to a third amplifier thatthe latter responds only to the differencesignal from the twofirst-mentioned amplifiers, the output of the third amplifier being alsoconnected to a counting unit. This can be realized, for instance, byconnecting the outputs of the two first-mentioned amplifiers to the endsof the primary winding of a transformer, the secondary winding of whichis connected to the said third amplifier. However, it is preferable tomake use of a wiring system in which the output of one of the first twoamplifiers is connected to the output of a reversal stage, the input ofwhich is connected to the output of the other amplifier, the output ofthe first amplifier being also connected to a counting unit by way of athird amplifier- Variations in the charge along the axis of the yarnthat are a result of those charges on the yarn, which give rise toconcentric axial-symmetrical equipotential surfaces, will induce equalvariations in the charge into the two groups of scanning members, Bymixing the amplified signals after the signal received from one of saidgroups has been converted such variations in the charge can be separatedby sifting. The chance of a slub passing the scanning members in such away that it excites a perfectly identical signal is neglectably small.

If the two groups of scanning members each comprise several scanningmembers that are so arranged that two of these members, each belongingto a different group, are always placed close together, the effect ofthe electrostatic potential planes being arranged irregulariy can bepractically neutralized without causing interference with the signalreceived from a passing slub.

Preferably an arrangement is applied in which the scanning members ofthe two groups are arranged alternately in a star-shaped pattern. Thisarrangement has been found to be the best possible means of avoidingunfavorable effects on the signals received from slubs. In order torealize this arrangement it is conceivable that straight scanningdevices may be inserted over equally long disstances in a ring ofinsulating material through the center of which the yarn is adapted torun.

According to the invention, however, a very simple solution can beobtained when a construction is used in which the two groups of scanningmembers are formed by two metal wires wound hclically, the helices beingbent into. the form of a circle at an intervals of half a pitch. Thisconstruction offers several advantages. Thus, the connections betweenthe scanning members in a group become very short. Moreover, the helicalarrangement of the metal wires renders it more probable for the slub tocome into contact with one of the helices.

The above arrangement of the scanning members in which two of saiddevices, each belonging to a different group, e always placed closetogether is also objectionable in that it causes neighboring scanningmembers to form a condenser the capacity of which attenuate theintensity of the difierence signal considerably. According to theinvent-ion, however, this disadvantage can be avoided by providing eachscanning member with one or more screening conductors. Where thescanning members are designed in the above-described shape of helicallywound metal wires, the screening arrangement according to the inventioncan be realized very conveniently by winding one or more insulated metalwires between the helices of the scanning members, the metal wireshaving the same helices as the scanning members and serving as screeningconductors.

In order to transmit a signal of the highest possible intensity to theamplifiers, it has been found necessary according to the invention forthe scanning members to be of a very low self-capacity. A satisfactoryembodiment of the amplifiers to which the scanning members are connectedis characterized by a high input impedance and a low output impedance,whereby the relaxation period of an incoming signal determined by theinput impedance and the capacity of the scanning members is at least aslong as the period necessary for a slub to pass the scanning deviceunder normal operating conditions.

[For the purpose of explaining the term relaxation period of an incomingsignal it is pointed out that the signal may be considered to be fed toan equivalent circuit of the amplifier input. This equivalent circuitconsists of a simple R-C (resistance-capacitance) wiring system. Of sucha system itis known that a voltage signal dies away in it proportionalto the function After a time t=R.C., the so-called relaxation time, thesignal is reduced by a factor 1/ e.

It is desirable that the said relaxation time is at least as long as thetime taken by a slub to pass the scanning member under normal operatingconditions. In this manner the charge of a passing slub is caused tobring about the greatest possible induct-ion charge on the amplifierinput.

In the case of a wiring arrangement allowing of a very satisfactory andinterference-free amplification of the signals received, each scanningdevice or group of scanning devices is connected, as a cathode follower,to the grid of an amplifying valve. Each scanning member is provided onboth sides with screening members, which are each or by groups connectedto the cathode of the amplifying valve whose grid is coupled to thescanning member provided with said screening members.

The above-described apparatus for signalling and registering theexistence of slubs on a running yarn or sheet of yarns may be fitted onor form part of many different textile machines, such as creels,winders, and coners.

This apparatus has proved to be of particular advantage in combinationwith drawtwisters for drawing yarns manufactured from thermoplasticlinear polymers such as, for example, polyamides, polyesters,polymethanes and copolymers, since it has been found that the majorityof slubs are obtained when the production process of such yarns is inthe drawing stage.

If the number of slubs can be determined immediately after drawing andprior to winding, the yarns wound to packages can be sorted in a simplemanner. It has been found that the number of slubs that may have beenproduced after counting, e.g. during winding or other additionaltreatments is negligibly small. Consequently, they no longer have anyessential influence on the quality of the end product.

In order that the invention may be more clearly understood therefollowsbelow, with reference to the accompanying drawings, a description of adrawtwister provided with a scanning device according to the invention.

In the drawings,

FIGURE 1 is a diagrammatic front View of a drawtwister showing ascanning member in position,

FIGURE 2 is a detail View of a scanning member,

FIGURE 3 is a diagrammatic view of the circuit for the amplification ofthe signals received, and

FIGURE 4- is a detailed diagrammatic representation of the introductioninto the amplifier circuit of a received signal.

Like reference characters indicate like parts throughout the severalviews of the drawings.

In FIGURE 1 the reference numeral 1 indicates a package of undrawn yarn.After this yarn has been drawn down, it is Wound onto another package 2mount ed on a conventional twisting spindle (not shown). To this end theundrawn yarn 3 runs from the package 1 through a guiding eyelet 4 to apair of feed rollers 5 and 6. From there it is pulled over the draw pins7 and 8 by a draw godet 9. After passing the draw pins 7 and- 8, theyarn 3 is wound a few times around the draw godet 9 and the guidingroller 19 and subsequently fed to the twisting spindle, through aneyelet 11, thus forming a yarn balloon 12 with the aid of a traveller 13of the twisting device and is wound onto the package 2.

Between the draw godet 9 and the eyelet 11 there are provided two threadguides 14 and 15, which keep the yarn 3 very accurately in a fixed path.Also between said two thread guides 14 and 15 there is a scanning memberor feeler 1d, repersented in detail on an enlarged scale in FIGURE 2.The feeler consists of a ring 17 of insulating material. The ring 17 isprovided with an aperture 18, through which a yarn 3 can be guidedintothe ring. The ring 17 is attached to a holder 19 by means of whichthe feeler 16 can be conveniently mounted in desired position. Thearrangement of the thread guides 14 and 15 relative to the feeler 16 issuch that a yarn 3, which is led along the guides 14 and 15, passesthrough the center of the ring 17.

Around the ring 17, six metal wires 29, 21, 22, 23, 24 and 25 are wounda few times according to a helical pattern. The wires 21 and 24. are ofbright copper, the others of enameled copper. The wires around the ring17 are all coated with a very thin layer of plastic material to preventthe ring from becoming dirty. The wires and 22 as well as the wires 23and 25 are connected in pairs and function as shielding wires.

FIGURE 2 shows a diagrammatic cross-section of a yarn thread with onebroken single filament 26. As will be seen, the so-called slub isobviously nearer to the metal wire windings than the unbroken filaments.Accordingly, the slub in passing through the ring 17 will induce acharge on one winding of the wires 21 or 24.

From the feeler 16 the signals, received either by the wire 21 or thewire 24, are fed to the identical amplifiers A or A respectively, towhich the wires are operatively connected, as shown in FZGURE 3. Theamplifiers 5 A and A are cathode followers and function as impedancetransformers, i.e. their input impedance is very high and their outputimpedance low.

Connected in series with the amplifier A is a reversal stage R whichefiects a completely uniform reversal of the output signal from theamplifier A Since the output impedance of the amplifiers A and A is low,it is possible for the following circuit elements to be connected tosaid amplifiers by means of comparatively long cables and be disposedelsewhere.

The output signal from the reversal stage R is mixed with that from theamplifier A As a result, all the noise signals produced by the slubs canbe practically eliminated. Moreover, it has been found that the wiringsystem is highly insensitive to external interferences. All signalsmeasured are subsequently transmitted to an amplifier stage A and fromthere they are finally passed to a counting unit C. This counting unit Cresponds in such a way that if two ends of a broken single filamentpass, only one slub is counted.

The shielding wires 20, 22, 23 and 25 are connected to the amplifierstages A and A as is shown in FIGURE 4.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of this invention.

What is claimed is:

1. Apparatus for signalling the existence of slubs in a travelling yarncomprising means for drawing the yarn whereby an electrostatic charge isplaced thereon, two thread guides for maintaining the travelling yarn ina fixed path, a scanning device positioned along the path of thetravelling yarn between the said thread guides and symmetrical inrelation to the yarn path, said scanning device comprising an evennumber of scanning members of electrically conductive material to whichthe electrostatic charge on the slubs in the textile material istransmitted, said scanning members being located at an equal distancefrom the axis of the yarn' path and being divided into first and secondgroups containing the same number of scanning members, first and secondamplifiers connected to said first and second scanning groupsrespectively, a third amplifier to which the outputs of the two saidamplifiers are connected in such a manner that only the differencesignalfrom the two said amplifiers is responded to by said third amplifier,and means connected to the output of said third amplifier for signallingthe presence of slubs.

2. An apparatus according to claim 1, characterized in that the outputof said second amplifier is connected to the input of a reversal stage,the output of which is connected to the output of said first amplifier,the output of said first amplifier being connected to the signallingmeans by way of said third amplifier.

3. An apparatus according to claim 1, characterized in that the groupsof scanning members are formed by two metal wires wound helically and atan interval of half a pitch, the helices being bent into the form of acircle.

4. An apparatus according to claim 1, characterized in that the scanningmembers are insulated from each other by one or more shieldingconductors.

5. An apparatus according to claim 3, characterized in that between thehelices of the scanning members insulated metal wires are wound of thesame helices as that of the scanning members, the metal wires serving asscreening conductors.

6. An apparatus according to claim 5, characterized in that the scanningmembers have a very low self-capacity.

7. An apparatus according to claim 1, characterized in that theamplifiers to which the scanning members are connected have a high inputimpedance and a low output impedance, whereby the relaxation time of anincoming signal determined by the input impedance and the capacity ofthe scanning members, is at least as long as the time necessary for aslub to pass the scanning member under normal operating conditions.

8. An apparatus according to claim 1, characterized in that a pluralityof scanning devices are employed and the scanning members ofsaid'scanning devices are connected to the grids of the amplifying valveof the amplifier, said amplifying valves being connected as a cathodefollower, and each scanning device being provided on both sides withscreening members, connected to the cathode of the amplifying valve thegrid of which is coupled to the scanning member provided with saidscreening members.

9. Apparatus for indicating irregularities in travelling textilematerial comprising means for conveying and guiding a textile materialalong a fixed path whereby an electrostatic charge is placed thereon, ascanning device supported alongside the path of moving textile material,said scanning device including an insulating member and at least twoconductors coiled helically about said member whereby the electrostaticcharge produced by any irregularity in the textile material may beinduced therein, an electronic amplifier connected to each of saidcoiled con References Cited by the Examiner UNITED STATES PATENTS2,010,683 8/35 Williams 206-65 2,295,795 9/42 Keeler 73-460 2,304,64512/42 Keeler 73-160 2,326,928 8/ 43 Courson 206-65 2,929,245 3/ 60Fischer 73160 RICHARD C. QUEISSER, Primary Examiner.

F. T. GARRETT, ROBERT L. EVANS. Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,187,568 June 8, 1965 Victor Emanuel Gonsalves et a1.

It is hereby certified that error appears in the above numbered patentreqiiring correction and that the said Letters Patent should read ascorrectedbelow.

Column 6, line 37, for "textile material" read traveling yarn Signed andsealed this 23rd day of November 1965.

(SEAL) Altest:

ERNEST W. SWIDER EDWARD J. BRENNER Almsting Officer Commissioner ofPatents

9. APPARATUS FOR INDICATING IRREGULARITIES IN TRAVELLING TEXTILEMATERIAL COMPRISING MEANS FOR CONVEYING AND GUIDING A TEXTILE MATERIALALONG A FIXED WHEREBY AN ELECTROSTATIC CHARGE IS PLACED THEREON, ASCANNING DEVICE SUPPORTED ALONGSIDE THE PATH OF MOVING TEXTILE MATERIAL,SAID SCANNING DEVICE INCLUDING AN INSULATING MEMBER AND AT LEAST TWOCONDUCTORS COILED HELICALLY ABOUT SAID MEMBER WHEREBY THE ELECTROSTATICCHARGE PRODUCED BY AN IRREGULARITY IN THE TEXTILE MATERIAL MAY BEINDUCED THEREIN, AN ELECTRONIC AMPLIFIER CONNECTED TO EACH OF SAIDCOILED CONDUCTORS TO RECEIVE THE ELECTROSTATIC CHARGE PRODUCED BY SUCHIRREGULARITY, MEANS FOR ELECTRONICALLY DIFFERENTIATING THE OUTPUTS OFSAID AMPLIFIERS TO PRODUCE A RESULTING SIGNAL AND ELECTRONIC MEANSRECEIVING AND RESULTING SIGNAL TO INDICATE THE PRESENCE OF SUCHIRREGULARITIES IN THE TEXTILE MATERIAL.